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Extract all integers from a given String

Last Updated : 23 Jul, 2025
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Given a string str, extract all integers words from it.

Example:

Input: str = "1Hello2   &* how  are y5ou"
Output: 1 2 5

Input: str = "Hey everyone, I have 500 rupees and I would spend a 100"
Output: 500 100

Approach: To solve this problem follow the below steps:

  1. Create a string tillNow, which will store all founded integers till now. Initialise it with an empty string.
  2. Now start traversing string str, and in each iteration:
    1. If a character is a number, add it to the string tillNow.
    2. Otherwise, check if the string tillNow is empty or not. If it isn't empty, then convert it to an integer and empty it after printing it.
  3. Now, after the loop ends, check again that if the string tillNow is empty or not. If it isn't then, convert it to integer and print it.

Below is the implementation of the above approach

C++ 
// C++ program for the above approach

#include <bits/stdc++.h>
using namespace std;

// Function to extract integers from
// the string str
void extractIntegers(string str)
{
    int n = str.size();

    // This variable will store each founded
    // integer temporarily
    string tillNow = "";

    for (int i = 0; i < n; i++) {

        // If current character is an integer, then
        // add it to string tillNow
        if (str[i] - '0' >= 0 and str[i] - '0' <= 9) {
            tillNow += str[i];
        }

        // Otherwise, check if tillNow is empty or not
        // If it isn't then convert tillNow to integer
        // and empty it after printing
        else {
            if (tillNow.size() > 0) {
                cout << stoi(tillNow) << ' ';

                tillNow = "";
            }
        }
    }

    // if tillNow isn't empty then convert tillNow
    // to integer and print it
    if (tillNow.size() > 0) {
        cout << stoi(tillNow) << ' ';
    }
}

// Driver Code
int main()
{
    string str = "Hey everyone, "
                 "I have 500 rupees and"
                 " I would spend a 100";
    extractIntegers(str);
}
Java 
// Java program for the above approach
class GFG{

// Function to extract integers from
// the String str
static void extractIntegers(char []str)
{
    int n = str.length;

    // This variable will store each founded
    // integer temporarily
    String tillNow = "";

    for (int i = 0; i < n; i++) {

        // If current character is an integer, then
        // add it to String tillNow
        if (str[i] - '0' >= 0 && str[i] - '0' <= 9) {
            tillNow += str[i];
        }

        // Otherwise, check if tillNow is empty or not
        // If it isn't then convert tillNow to integer
        // and empty it after printing
        else {
            if (tillNow.length() > 0) {
                System.out.print(Integer.parseInt(tillNow) +" ");

                tillNow = "";
            }
        }
    }

    // if tillNow isn't empty then convert tillNow
    // to integer and print it
    if (tillNow.length() > 0) {
        System.out.print(Integer.parseInt(tillNow) +" ");
    }
}

// Driver Code
public static void main(String[] args)
{
    String str = "Hey everyone, "
                 +"I have 500 rupees and"
                 +" I would spend a 100";
    extractIntegers(str.toCharArray());
}
}

// This code is contributed by 29AjayKumar
Python3 
# Python3 program for the above approach

# Function to extract integers from
# the string str
def extractIntegers(string) :

    n = len(string);

    # This variable will store each founded
    # integer temporarily
    tillNow = "";

    for i in range(n) :

        # If current character is an integer, then
        # add it to string tillNow
        if (ord(string[i]) - ord('0') >= 0 and ord(string[i]) - ord('0') <= 9) :
            tillNow += string[i];

        # Otherwise, check if tillNow is empty or not
        # If it isn't then convert tillNow to integer
        # and empty it after printing
        else :
            if (len(tillNow) > 0) :
                print(int(tillNow),end = ' ');

                tillNow = "";

    # if tillNow isn't empty then convert tillNow
    # to integer and print it
    if (len(tillNow) > 0) :
        print(int(tillNow),end = ' ');


# Driver Code
if __name__ == "__main__" :

    string  = "Hey everyone, I have 500 rupees and I would spend a 100";
    
    extractIntegers(string);

    # This code is contributed by AnkThon
C# 
// C# program for the above approach
using System;
class GFG
{

    // Function to extract integers from
    // the String str
    static void extractIntegers(char[] str)
    {
        int n = str.Length;

        // This variable will store each founded
        // integer temporarily
        String tillNow = "";

        for (int i = 0; i < n; i++)
        {

            // If current character is an integer, then
            // add it to String tillNow
            if (str[i] - '0' >= 0 && str[i] - '0' <= 9)
            {
                tillNow += str[i];
            }

            // Otherwise, check if tillNow is empty or not
            // If it isn't then convert tillNow to integer
            // and empty it after printing
            else
            {
                if (tillNow.Length > 0)
                {
                    Console.Write(int.Parse(tillNow) + " ");

                    tillNow = "";
                }
            }
        }

        // if tillNow isn't empty then convert tillNow
        // to integer and print it
        if (tillNow.Length > 0)
        {
            Console.Write(int.Parse(tillNow) + " ");
        }
    }

    // Driver Code
    public static void Main(String[] args)
    {
        String str = "Hey everyone, "
                     + "I have 500 rupees and"
                     + " I would spend a 100";
        extractIntegers(str.ToCharArray());
    }
}

// This code is contributed by Saurabh Jaiswal
JavaScript 
<script>
// Javascript program for the above approach

// Function to extract integers from
// the string str
function extractIntegers(str) {
  let n = str.length;

  // This variable will store each founded
  // integer temporarily
  let tillNow = "";

  for (let i = 0; i < n; i++) {

    // If current character is an integer, then
    // add it to string tillNow
    if (str[i].charCodeAt(0) - '0'.charCodeAt(0) >= 0 && str[i].charCodeAt(0) - '0'.charCodeAt(0) <= 9) {
      tillNow += str[i];
    }

    // Otherwise, check if tillNow is empty or not
    // If it isn't then convert tillNow to integer
    // and empty it after printing
    else {
      if (tillNow.length > 0) {
        document.write(tillNow + ' ');
        tillNow = "";
      }
    }
  }

  // if tillNow isn't empty then convert tillNow
  // to integer and print it
  if (tillNow.length > 0) {
    document.write(tillNow + ' ');
  }
}

// Driver Code
let str = "Hey everyone, I have 500 rupees and I would spend a 100";
extractIntegers(str);

// This code is contributed by gfgking.
</script>

Output
500 100

Time Complexity: O(N)
Auxiliary Space: O(N)

Approach 2: Using Regex

C++ 
#include <bits/stdc++.h>
using namespace std;

void extractIntegers(string sentence)
{

    // Split string using regex so only the string will
    // be available that only made up of digits Regex
    // Explanation ->
    // [^...]+ matches the all character except present
    // in square bracket with as many as possible
    // characters {4} -> To match the string whose
    // length is four
    stringstream ss(sentence);
    string temp;
    vector<int> integers;
    while (ss >> temp) {
        if (temp[0] >= '0' && temp[0] <= '9') {
            integers.push_back(stoi(temp));
        }
    }
  
    // Print the Extracted Integers
    for (int i : integers)
        cout << i << " ";
}

int main()
{
    string sentence1 = "Hey everyone I have 500 rupees and "
                       "I would spend a 100";
    extractIntegers(sentence1);
    return 0;
}

// This code is contributed by akashish__
Java 
/*package whatever //do not write package name here */

import java.util.*;

class GFG {

    static void extractIntegers(String sentence)
    {

        // Split string using regex so only the string will
        // be available that only made up of digits Regex
        // Explanation ->
        // [^...]+ matches the all character except present
        // in square bracket with as many as possible
        // characters {4} -> To match the string whose
        // length is four

        String splittedWords[] = sentence.split(
            "[^0-9]+"); // Can also split with "[a-zA-Z()._
                        // -]+{4}"

        // Print the Extracted Integers
        for (String i : splittedWords)
            System.out.print(i + " ");
    }

    public static void main(String[] args)
    {

        String sentence1
            = "Hey everyone I have 500 rupees and I would spend a 100";
        extractIntegers(sentence1);
    }
}
Python3 
import re

def extract_integers(sentence):
    # Split string using regex so only the string will
    # be available that only made up of digits Regex
    # Explanation ->
    # [^...]+ matches the all character except present
    # in square bracket with as many as possible
    # characters {4} -> To match the string whose
    # length is four
    splitted_words = re.findall(r'\b\d+\b', sentence)

    # Print the Extracted Integers
    for i in splitted_words:
        print(i, end = " ")

sentence1 = "Hey everyone I have 500 rupees and I would spend a 100"
extract_integers(sentence1)

# This code is contributed by akashish__
C# 
using System;
using System.Linq;
using System.Text.RegularExpressions;

public class GFG {

  static void extractIntegers(string sentence)
  {
    // Split string using regex so only the string will
    // be available that only made up of digits Regex
    // Explanation ->
    // [^...]+ matches the all character except present
    // in square bracket with as many as possible
    // characters {4} -> To match the string whose
    // length is four

    string[] splittedWords
      = Regex.Split(sentence, "[^0-9]+");
    // Print the Extracted Integers
    foreach (string i in splittedWords) {
      if (!string.IsNullOrEmpty(i)) {
        Console.Write(i + " ");
      }
    }
  }

  static public void Main()
  {
    string sentence1
      = "Hey everyone I have 500 rupees and I would spend a 100";
    extractIntegers(sentence1);
  }
}

// this code is contributed by akashish__
JavaScript 
function extractIntegers(sentence)
{

    // Split string using regex so only the string will
    // be available that only made up of digits Regex
    // Explanation ->
    // [^...]+ matches the all character except present
    // in square bracket with as many as possible
    // characters {4} -> To match the string whose
    // length is four
    let splittedWords = sentence.match(/\b\d+\b/g);// Can also split with "[a-zA-Z()._
                        // -]+{4}"

    // Print the Extracted Integers
    for (let i = 0; i < splittedWords.length; i++) {
        console.log(splittedWords[i], " ");
    }
}

let sentence1 = "Hey everyone I have 500 rupees and I would spend a 100";
extractIntegers(sentence1);

// This code is contributed by akashish__

Output
 500 100

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